It is known in the art to perform corneal ablation by means of wavefront-guided refractive laser surgery. Typically a wavefront sensor measures an aberration map and its position relative to anatomical landmarks, which can be intrinsic or externally applied features. Aberration data, sometimes along with geometric registration information, can be transferred directly to a treatment excimer laser, which is typically used to perform the ablation.
In ophthalmic devices, the positioning of a measuring or ablation device a known distance from, and correctly aligned to, an eye, such that the device can be therapeutically effective, is of great importance. In some systems the eye must be centered and in clear focus for interaction of the image with an operator. It can also be important for a laser beam to come to focus at a predetermined plane with respect to the eye, for example, in an excimer laser system, or to have the eye positioned for an effective subsequent measurement of the eye, for example, a wavefront measurement.
Among the known techniques for assisting in positioning an ophthalmic device are the breaking of a plurality of light beams, such as infrared light beams, by the corneal apex, and the projection onto the cornea of a plurality of light beams, which can subsequently be analyzed either automatically or by an operator to assess accuracy of eye positioning. If the eye is deemed not to be in a therapeutically effective position, then the device and/or head/eye can be moved so as to reposition the eye optimally or to within defined acceptable tolerances.
Known current approaches to solving the positioning problem are typically subject to error and require intervention by an operator and/or additional hardware. Therefore, it would be advantageous to provide a system and method for improving accuracy and automation in eye alignment, without the need for human operator input or for additional hardware.